Electrodeposition of zinc



United States Patent 3,318,787 ELECTRODEPOSITION 0F ZINC Gustav Rindt, St. Clair Shores, and Donald H. Becking,

Birmingham, Mich, assignors to The Udylite Corporation, Warren, Mich, a corporation of Delaware N0 Drawing. Filed Feb. 7, 1964, Ser. No. 343,220 30 Claims. (Cl. 204--55) This invention relates to improvements in the electrodeposition of zinc, and is particularly concerned with the electrodeposition of bright zinc from alkaline cyanide zinc baths which contain as brightening agents bathsoluble quaternary nitrogen compounds containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamides, carboxy and nitrile groups, hereinafter more fully described.

The electrodeposition of zinc from alkaline cyanide zinc solutions is widely used to produce coatings which protect iron and steel by sacrificial cathodic protection. It is an outstanding metal for providing this desirable protection.

To augment this desirable property of providing excellent corrosion protection, it is also advantageous in many applications that the electrodeposited zinc have a pleasing luster that does not tarnish too rapidly, and many brighteners and addition agents have been developed to improve the appearance of the electroplated zinc obtained from cyanide zinc baths which normally yield dull gray plate.

It is desirable to obtain the lustrous zinc plate in as short a plating time as possible and with uniform brightness over the entire plating range, and without roughness, excessive build-up of plate on high current density areas, or poor coverage in low current density areas. The qualities just enumerated result in a savings in expenditure on plating equipment and increase the plant productivity. Furthermore, it is highly desirable to achieve the qualities enumerated above at the lowest cost and with the least operational troubles.

In the present state of the art, it is quite common to subject the bright zinc electrodeposits to oxidizing acid dips such as chromic acid dips to produce passive films for further protective effects and for superior lacquer and paint adhesion. It is also quite common to also subject the zinc electrodeposits to phosphate type dips to produce films giving rise to improved adhesion of paint coatings to the zinc surface. It is very important in many cases that the bright zinc electrodeposits can be subjected to such dips with no resultant discoloration of the zinc electrodeposit and with good uniformity of the films.

The addition agents for alkaline cyanide zinc electroplating baths used in accordance with the prior art are subject to certain disadvantages. For example, inorganic addition agents used in the rather high concentrations found in the prior art have a tendency to cause an undesirable appearance of the zinc electrodeposit when subsequently subjected to the commonly used passivating dips. Addition agents such as aromatic aldehydes, polyvinyl alcohol, modified polyvinyl alcohols such as oxidized polyvinyl alcohol, and ethoxylated derivatives, various grades of gelatin and glue, used alone or in combination with each other, still leave much to be desired, in that the current density range at which acceptable bright zinc electroplate is produced is narrow and limited to the lower current density range of the bat Over the years, a great deal of work has been done to promote the increased use of this important metal as an electrodeposited coating. One of the best means to achieve this is by the development of improved addition agents to obtain brighter zinc deposits over a broad plating range from the electroplating bath. The improved addition agents should also provide an electroplating bath that is relatively easy to operate and economical to use.

It has now been found that bath-soluble quaternary nitrogen compounds containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamides, carboxy and nitrile (cyano) groups make possible the electrodeposition of smooth bright zinc deposits from alkaline cyanide zinc baths over a wide cathode current density range. Furthermore, they cooperate to an unusual degree with other well known addition agents for alkaline zinc baths such as the aforementioned aryl aldehydes, gelatin and glue of various grades, polyvinyl alcohol and modified polyvinyl alcohol, such as oxidized polyvinyl alcohol, ethoxylated polyvinyl alcohol, peptones, formaldehyde, and very specifically with very small concentrations of the inorganic addition agent manganese, also with molybdenum oxide, trivalent chromium, iron and with combinations of these prior art addition agents, to give very high brightness over a broad current density plating range.

In Table I are listed examples of some of the preferred new addition agents for alkaline zinc cyanide electroplating solutions. These addition agents or bri hteners are bath soluble quaternaries of certain substituted pyridines, especially the quaternaries of nicotinic acid esters and amides, including bis-quaternaries. These new addition agents for alkaline zinc plating baths may be classified with respect to their scope by the following general formula 0 ia] L n,

N A Ri Y where R is a radical selected from the group consisting of hydroxy and alkoxy groups, alkenoxy, alkynoxy and substituted alkoxy, alkenoxy and alkynoxy groups, amide and substituted amide groups. For example, R may be -OCH OC H OC H CI, -OC H -OC H 3 3 e 5, OCH2CGH5: 2 4 )X -O(C H O) H, O'(C H O) Cl, etc., where x=1 to about at least 10. R may be NH --NHCH a)2, NHC2H5: 2 5)2, s 5 NH(C H.,O) 'H, NH(C H O),,H, etc. R may be alkyl, alkylene, alkene, alkyne, alkyl phenyl, phenyl, and

alkyl naphthyl radicals, and the alkyl and aryl groups may have specific substituting groups such as halogen, nitro, nitroso, hydroxy, alkoxy, carboxy, cyano, sulfo, ester, methyl, ethyl, etc. These same specific substituting groups may be used for R on the carbon of the pyridine rings. R represents the cyano radical. A represents an anion or an anionic linkage such as chloro, bromo, iodo, fluoro, sultone, methosulfate, ethosulfate, hydroxide, oxide, betaine or sulfobetaine anionic linkage. The subscripts n 11 and n represent integers which together may total 1 to 5, when n is l to 5 inclusive then 11 :0, and n can be 0 to 4, and n is 1 when 11 is zero, and when n is zero and n is zero, it is preferred that R contains an ester group as in N-ethylcarboxymethyl, Z-methyl pyridinium chloride (Example 35 in Table I). In this latter case, R =the 2-methyl group on the pyridine ring, that is, it (Example 35) is a picolinium quaternary.

The most important substituting groups on the carbon of the pyridine rings are the carboxylic ester and carboxamide groups, next is the nitrile group. The character of the anion A is not important for the brightening action, and wherether A is chloride, bromide, hydroxide, methosulfate, ethosulfate, or is in oxide, sultone or betaine or sulfobetaine form of anionic linkage is not of great significance. The subscript y=1 or 2, and when y =2, the radical R joins two pyridine rings as his type quaternaries. If n +n +n =0, then R should contain a carboxy or ester group for best results. Allyl bromide, benzyl chloride, methyl or ethyl chloroacetate quaternaries of methyl, ethyl or propyl nicotinates give excellent brightening results in the alkaline zinc baths, and the quaternaries of methyl, ethyl, propyl and allyl chloroacetates or chloropropionates give excellent results not only with pyridine and the substituted pyridines, but also with triethanolamine, triethylamine, triallylamine, tetramethyl ethylene diamine, and other amines.

While pyridine itself has no perceptible brightening action in the alkaline ZlIlC cyanide baths, the compounds of Table I, which are best defined as bath-soluble pyridine quaternary compounds which contain at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamides, carboxy and nitn'le groups, on the other hand, are very effective brighteners.

Excellent examples of very effective zinc brighteners are Compounds 4 and 16 of Table I C O CH3 0 ONHz which are respectively the benz-yl chloride quaternary of methyl nicotinate and the methyl chloroacetate quaternary of nicotinamide.

TABLE I N-allyl 3-ethyl carboxylate pyridinium bromide N-allyl 2-ethyl carboxylate pyridinium bromide N-allyl 4-methyl carboxylate pyridinium bromide N-benzyl 3-methyl carboxylate pyridinium chloride N-benzyl 4-methyl carboxylate pyridinium chloride (6) N-benzyl Z-methyl carboxylate pyridinium chloride (7) N-sulfopropyl 3-methyl carboxylate pyridinium sulfate (8) N-p-chlorobenzyl 3-methyl carboxylate pyridinium chloride (9) N-p-nitrobenzyl 3-methyl carboxylate pyridinium bromide (10) N-allyl 2,4,6-trimethyl carboxylate pyridinium bromide (11) N-allyl 2,4-dimethyl carboxylate pyridinium bromide (12) N-benzyl 4-bromo 3-methyl carboxylate pyridinium chloride (13) N-benzyl 6-methyl 2-methyl carboxylate pyridinium chloride (14) N-methyl 3-ethyl carboxylate pyridinium methosulfate (15 N-ethyl 3-methyl carboxylate pyridinium ethosulfate (l6) N-methyl acetate 3-carboxamide pyridinium chloride (N-methylcarboxymethyl 3-carboxamide pyridinium chloride) (17) N-allyl 3-carboxamide pyridinium bromide (18) N-benzyl 3-carboxamide pyridinium bromide (19) N-methylene naphthalene 3-methyl carboxylate pyridinium chloride (20) N-alpha-acetophenone 3-methyl carboxylate pyridinium chloride (21) Bis-N,N-2-ethane 3,3'-methyl carboxylate pyridinium bromide (22) N-allyl 2-butyl carboxylate pyridinium bromide (23) N-propargyl 3-methyl carboxylate pyridinium bromide (24) N-isopropyl 4-isopropyl carboxylate pyridinium bromide (25) N-sulfoethane 4-methyl carboxylate pyridinium bromide (26) N-allyl-3-N-diethyl carboxamide pyridinium bromide (27) N-sulfobutane 4-bromo 2-methyl carboxylate pyridinium bromide (28) N,N'-bis-l,4-xylylene-3,3'-rnethyl carboxylate pyridinium chloride (29) N,N-bis-dimethyl phenyl ether, 3,3-methyl carboxylate pyridinium chloride (30) N-methyl phenyl ether-3-methyl carboxylate pyridinium chloride (31) N-ethanol 3-ethyl carboxylate pyridinium chloride (32) N-ethylcarboxymethyl 3-ethyl carboxylate pyridinium chloride (N-ethyl acetate 3-ethyl carboxylate pyridinium chloride) (33) N-carboxymethyl 3-ethyl carboxylate pyridinium chloride (34) N-carboxyethyl 3-ethyl carboxylate pyridinium chloride (35) N-ethylcarboxymethyl alpha picolinium chloride (36) N-allylacetate pyridinium chloride (37) N-acetamide 3-ethyl carboxylate pyridinium chloride (38) N-propionitrile 3-methyl carboxylate pyridinium chloride In order to more fully describe the use of the novel addition agents for the zinc baths, the following illustrative examples using, for example, certain of the compounds of Table I are given.

In Table II is given the bath composition and the operating conditions used to illustrate the new alkaline zinc bath addition agents of this invention.

The zinc deposits were plated on panels of cold-rolled steel after which they were removed from the Hull cell, rinsed in clear water, immersed in a solution of about 0.25% by volume of concentrated nitric acid for about 10 seconds to observe the efiect of the bright dip, rinsed in clear water, and dried. Other acidic oxidizing bright dips could have, of course, been used instead of the above mentioned nitric acid bright dip to observe the required results.

While the novel addition agents of this invention are effective in any commercially operable alkaline cyanide zinc plating bath, as a basic plating solution, it is preferred to use the well known cyanide zinc plating bath composition and operating conditions shown in Table II. This bath composition can be varied as required for special purposes in accordance with the now known skill in the art. For example, for better coverage in deep recesses, the metal content can be decreased, and the cyanide content increased. This, however, is accomplished at the expense of an over-all decrease in cathode efficiency.

TABLE II Bath composition: Concentration, grams/liter Zinc oxide 42.0 Sodium cyanide 82.5 Sodium hydroxide 75.0

Operating conditions Standard 267 ml. Hull cell:

Temperature F 75 Operating current amps 2 Plating time minutes 10 Example I Example II To a cyanide zinc plating hath made up and operated as above described in Table II there was added another novel addition agent of this invention, N-benzyl 3-methyl carboxylate pyridinium chloride in a concentration of 0.35 gram/ liter. Zinc deposits plated on Hull cell panels from this bath were bright from current densities of above 100 amps/sq. ft. to about 4 amps/sq. ft. The brightness of the deposit was improved after the as plated deposit was subjected to the previously described dilute nitric acid bright dip.

Example III To an alkaline cyanide zinc electroplating solution made up and operated as described in Table II there was added the following: 0.37 gram/liter N-allyl 2-ethyl carboxylate pyridinium bromide and 0.11 gram per liter polyvinyl alcohol. Zinc deposits plated on Hull cell panels from this bath were superior in brightness to any of those so far described. The bright plate range was also superior to any of the deposits so far described, extending from the high current density edge of the Hull cell panel to the low current density edge of the panel. At the very lowest current density area some imperfection in the smoothness of the deposit could be noticed.

Example IV To the cyanide zinc plating solution made up and operated as described in Table II there was added the following example of yet another novel addition agent of this invention, 0.25 gram/liter bis-1,4-xylylene-3,3-methyl carboxylate pyridinium chloride and 0.11 grams per liter polyvinyl alcohol and 0.37 gram/liter oxidized ethoxylated polyvinyl alcohol. Zinc deposits plated on Hull cell panels from this bath were superior to those obtained under Example III in that the zinc deposit in the lowest current density area was now smooth and fully bright. The brightness of the zinc deposit was further improved after subjecting it to the dilute nitric acid bright dip as described above.

Example V To an alkaline cyanide zinc electroplating solution made up and operated as described in Table II, there was added 0.25 gram/liter N-benzyl 3-carboxamide pyridinium bromide, and 0.12 gram/ liter polyvinyl alcohol. Zinc deposits plated on Hull cell panels from this bath had a bright current density range from the extreme high current density edge of the panel to the low current density edge of the panel.

Example VI To the cyanide zinc plating solution made up and operated as described in Table II, there was added the following, 0.37 gram/liter N-benzyl 3-ethyl carboxylate pyridinium chloride, and 0.15 gram/liter oxidized polyvinyl alco hol. Zinc deposits plated on Hull cell panels from this bath were bright over abroad current density range. The brightness of the zinc deposit was further improved after subjecting it to the dilute nitric acid bright dip as described above.

Example VII To a cyanide zinc solution made up and operated as described in Table II, there was added the following to further illustrate the novel features inherent in this invention, 0.28 gram/liter N-benzyl 3-methyl carboxylate pyridinium chloride, and 0.2 gram/liter glue. Zinc deposits plated on Hull cell panels from this bath had a bright current density range from about 80 amps/sq. ft. to the lowest current density edge of the panel. .The deposit was exceptionally bright at the lowest current density edge of the panel and the coverage was excellent. The characteristics of the deposit indicate the use of this combination of addition agents where the electroplating of parts in bulk barrel plating is to be carried out.

0 Example VIII To an alkaline cyanide zinc electroplating hath made up and operated as described in Table II there was added 0.28 gram/liter N-allyl 3-ethyl carboxylate pyridinium bromide, 0.17 gram/ liter glue, 0.24 gram per liter anisic aldehyde bisulfite and 0.05 gram/liter gelatin. Zinc deposits plated on Hull cell panels from this bath were superior in brightness to those produced in Example VII and the bright current density range was extended to about amps/sq. ft.

While we generally prefer to use the bath-soluble quaternaries of the substituted pyridines in the amounts of about 0.1 gram/liter to about 0.8 gram/liter and the amounts shown in the above examples are considered to be about the optimum amounts, it shall be understood that the quantities used may be greatly varied. To be more specific, we would use concentrations of the quaternaries of the substituted pyridines as low as about 0.005 gram/ liter when maximum operational concentrations of glue, aromatic aldehydes, polyvinyl alcohol, modified polyvinyl alcohol, etc, are present in the alkaline cyanide zinc baths. However, if no other zinc brighteners were present, it is possible to use concentrations as high as about 5 grams/ liter.

It will be appreciated that in general it will be found most convenient to dissolve the materials used as addition agents in water solutions to dispense them in a form more convenient to be added to a cyanide zinc electroplating solution, although this is not absolutely necessary. It will also be appreciated that in all cases where the aforementioned examples contain materials other than the quaternaries of the substituted pyridines, that if the substituted pyridines were to be omitted, the resultant zinc deposits from these solutions under the same operating conditions are very much inferior to those that are obtained when the above mentioned quaternaries of the substituted pyridines are present.

It will also be understood that the above specific examples are illustrative of the invention and that one skilled in the art may use the quaternaries of the substituted pyridines, with other combinations of the protective colloids, aromatic aldehydes, polyvinyl alcohol, modified polyvinyl alcohols, manganese, trivalent chromium, molybdenum, iron, in widely varying proportions without departing from the spirit of this invention or its teachings. However, it must be emphasized that apart from the quaternaries of the substituted pyridines the afore-mentioned organic addition agents and metals constitute no part of this present invention except in the conjoint use of these compounds or metals with the quaternaries of the substituted pyridines.

Metals such as manganese in the form of a manganese salt can be used in conjunction with the quaternaries illustrated in ,Table I, however, only very small concentrations are necessary to secure beneficial effects. For example, only about 0.005 to 0.1 gram/liter of manganese sulfate need be used, unlike the much larger concentrations usually necessary (see Westbrook United States Patent 2,080,520, issued May 18, 1937, and United States Patent 2,218,734, issued Oct. 22, 1940). The manganous salt can be used in the low concentrations in any one of the above eight cited bath examples with good results under prolonged use. Iron in the form of a ferrous or ferric salt is also beneficial in conjunction with the quaternaries of Table I. The more potent metal brighteners molybdenum oxide, and trivalent chromium (United State Patent 2,218,734) cooperate with low conccntrations of the quaternaries of Table I, but do not give much enhanced brightness with the: higher concentrations of the quaternaries. The organic compounds that cooperate excellently with the quaternaries exemplified in Table I are the type represented by bath-soluble polyvinyl compounds such as polyvinyl alcohols and modified polyvinyl alcohols such as oxidized polyvinyl alcohol (Wernlund US. 2,928,800, Mar. 15, 1960),

ethoxylated polyvinyl alcohol and oxidized ethoxylated polyvinyl alcohol. These polyvinyl alcohols and moditied polyvinyl alcohols may be present in the baths in conjunction with the quaternaries exemplified in Table I, in a total concentration of about 0.005 to about 0.5 gram/liter. When metals such as manganese or iron or both are used in low concentrations in conjunction with the quaternaries of Table I, or in their combinations with the polyvinyl alcohols or modified polyvinyl alcohols, it is desirable to use sequestering agents such as the ethylene diamine tetracetates, nitrilotriacetates, glucoheptosaminic acid salts, N,N bis (2 hydroxyethyl) :glycinate, etc., in concentrations of about 0.1 to about 10 grams/liter, to keep the dissolved manganese especially, or dissolved iron or both in solution. Gluconates, and citrates also help in sequestering when metal brighteners are used in the alkaline cyanide zinc baths in conjunction with the compounds of Table I.

The protective colloid gelatin or impure gelatin (glue) cooperates with the bath-soluble quaternaries of substituted pyridines when these gelatin materials are used in concentrations of 0.005 to about 0.3 gram/liter. The aromatic aldehydes such as anisic aldehyde and piperonal (heliotropin) cooperate with the quaternaries when these aldehydes are used in a concentration of 0.005 to about 0.5 gram/liter.

While the pyridine quaternaries of Table I represent the most effective embodiments of this invention, nevertheless, as already mentioned the bath-soluble quaternaries of other amines such as triethylamine, mono-, diand triethanolamine, N,N,N,N-tetramethyl ethylene diamine, hexamethylene tetramine, trimethylamine, triallylamine, dimethyl aniline, tri-isopropylamine, etc., also give good brightening when these amines are quaternized especially with methyl or ethyl or propyl chloroacetates or chloropropionates or with alpha chloroacetamide or beta chloropropionitrile. All of these quaternaries for use in alkaline cyanide zinc electroplating baths can be classified as bath-soluble quaternary nitrogen compounds containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamides, carboxy and nitrile groups, and to be used in a concentration range of 0.005 to about 5 grams/liter, with 0.1 to 0.8 gram/liter usually the optimum amounts. Outstanding among these compounds are the quaternaries of methyl, ethyl, or propyl nicotinate esters.

What is claimed is:

1. A bath for the electrode-position of lustrous zinc comprising an aqueous alkaline cyanide zinc bath containing dissolved therein in a concentration of about 0.005 to about 5 grams per liter of a bath-soluble quaternary nitrogen compound containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamide, carboxy and nitrile groups.

2. A bath as claimed in claim 1 wherein said quaternary is N-allyl,3-ethyl carboxylate pyridinium bromide.

3. A bath as claimed in claim 1 wherein said quaternary is N-rnethyl carboxymethyl 3-ethyl carboxylate pyridinium chloride.

4. A bath as claimed in claim 1 wherein said quaternary is N-benzyl,3-ethyl carboxylate pyridinium chloride.

5. A bath as claimed in claim 1 wherein said quaternary is bis-1,4-xylene-3,3-ethyl carboxylate pyridinium chloride.

6. A bath as claimed in claim 1 wherein said quaternary is a quaternary of ethyl nicotinate.

7. A bath as claimed in claim 1 wherein said quaternary is a quaternary of methyl nicotinate.

8. A bath as claimed in claim 1 wherein said quaternary is a quaternary of propyl nicotinate.

9. A bath as claimed in claim 1 wherein there is also present in said bath a bath-soluble polyvinyl compound selected from the class of polyvinyl alcohol, oxidized polyvinyl alcohol, ethoxylated polyvinyl alcohol and oxidized ethoxylated polyvinyl alcohol, said bath-soluble poly-vinyl compound being present in a concentration of about 0.005 to about 0.5 gram/liter.

10. A bath as claimed in claim 1 wherein there is also present in said bath a manganous salt in a concentration of about 0.005 to about 0.1 gram/liter.

11. A bath as claimed in claim 1 wherein there is also present in said bath an iron salt in a concentration of about 0.005 to about 0.1 gram/liter.

12. A bath as claimed in claim 1 wherein there is also present in said bath a gelatin colloid in a concentration of about 0.005 to about 0.3 gram/ liter.

13. A bath as claimed in claim 1 wherein there is also present in said bath anisic aldehyde in a concentration of about 0.005 to about 0.5 gram/liter.

14. A bath as claimed in claim 1 wherein there is also present in said bath piperonal in a concentration of about 0.005 to about 0.5 gram/liter.

15. A method for the electrodeposition of lustrous zinc comprising the step of electrodepositing zinc from an aqueous alkaline cyanide zinc bath containing dissolved therein in a concentration of about 0.005 to about 5 grams/liter of a bath-soluble quaternary nitrogen compound containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamide, carboxy, and nitrile groups.

16. A method as claimed in claim 15 and wherein said quaternary is N-allyl,3-ethyl carboxylate pyridinium bromide.

17. A method as claimed in claim 15 and wherein said quaternary is N-methyl carboxymethyl 3-ethyl carboxylate pyridinium chloride.

18. A method as claimed in claim 15 and wherein said quaternary is N-benzyl,3-ethyl carboxylate pyridinium chloride.

19. A method as claimed in claim 15 wherein said quaternary is bis-l,4-xylylene-3,3-ethyl carboxylate pyridinium chloride.

20. A method as claimed in claim 15 and wherein said quternary is a quaternary of ethyl nicotinate.

21. A method as claimed in claim 15 and wherein said quaternary is a quaternary of methyl nicotinate.

22. A method as claimed in claim 15 and wherein said quaternary is a quaternary of propyl nicotinate.

23. A method as claimed in claim 15 and wherein there is also present in said bath a bath-soluble polyvinyl compound selected from the class of polyvinyl alcohol, oxidized polyvinyl alcohol, ethoxylated polyvinyl alcohol and oxidized ethoxylated polyvinyl alcohol, said bath-soluble polyvinyl compound being present in the bath in a concentration of about 0.005 to about 0.5 gram per liter.

24. A method as claimed in claim 15 and wherein there is also present in said bath a manganous salt in a concentration of about 0.005 to about 0.1 gram/ liter.

25. A method as claimed in claim 15 and wherein there is also present in said bath an iron salt in a concentration of about 0.005 to about 0.1 gram/liter.

26. A method as claimed in claim 15 and wherein there is also present in said bath a gelatin colloid in a concentration of about 0.005 to about 0.3 gram/ liter.

27. A method as claimed in claim 15 and wherein there is also present in said bath anisic aldehyde in a concentration of about 0.005 to about 0.5 gram/ liter.

28. A method as claimed in claim 15 and wherein there is also present in said bath piperonal in a concentration of about 0.005 to about 0.5 gram/ liter.

29. A bath for electrodeposition of lustrous zinc comprising an aqueous alkaline cyanide zinc bath containing dissolved therein in a concentration of about 0.005 to about 5 grams per liter of a bath soluble pyridinium quaternary compound containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, substituted carboxamide, carboxy and nitrile groups.

10 30. A method for the electrodeposition of lustrous zinc References Cited by the Examiner comprising the step of electrodepositing zinc from an UNITED STATES PATENTS aqueous alkaline cyanide zinc bath containing dissolved 2 842 488 7/1958 S trauss et a1 204-55 X thereln in a concentratlon of ebout 0.005 to about 5 2,900,313 8/1959 Saubestre et a1 204 55 X grams/liter of a bath-soluble pyridinium quaternary com- 5 2 928 800 3/1960 Wemlund X pound containing at least one substituting group selected from the class consisting of carboxylic ester, carboxamide, JOHN MACK, Primary Examlner' substituted carboxamide, carboxy, and nitrile groups. G. KAPLAN, AssistantExaminer. 

1. A BATH FOR THE ELECTRODEPOSITION OF LUSTROUS ZINC COMPRISING AN AQUEOUS ALKALINE CYANIDE ZINC BATH CONTAINING DISSOLVED THEREIN IN A CONCENTRATION OF ABOUT 0.005 TO ABOUT 5 GRAMS PER LITER OF A BATH-SOLUBLE QUATERNARY NITROGEN COMPOUND CONTAINING AT LEAST ON SUBSTITUTING GROUP SELECTED FROM THE CLASS CONSISTING OF CARBOXYCLIC ESTER, CARBOXAMIDE, SUBSTITUTED CARBOXAMIDE, CARBOXY AND NITRILE GROUPS. 